Java实现多线程的四种实现方式-白红宇

Java实现多线程的四种实现方式

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发布时间：2019-06-26

本文共 3612 字，大约阅读时间需要 12 分钟。

以计算0到1000之间的和为例

import java.util.ArrayList;import java.util.LinkedList;import java.util.List;import java.util.concurrent.*;import java.util.concurrent.atomic.AtomicInteger;public class Main {//求1~N全部整数的和，会上溢int N = (int) 1e8;int threadSize = 5;/** * 最原始最基础的方式：使用thread，自定义并发 */class ThreadJoin {    void go() {        Thread[] a = new Thread[threadSize];        //每个线程应该干多少活        int per = (int) Math.ceil(N * 1.0 / a.length);        final AtomicInteger s = new AtomicInteger(0);        for (int i = 0; i < a.length; i++) {            int ii = i;            a[i] = new Thread(() -> {                int sum = 0;                for (int j = ii * per; j < Math.min(ii * per + per, N); j++) {                    sum += j;                }                s.addAndGet(sum);            });            a[i].start();        }        for (Thread i : a)            try {                i.join();            } catch (InterruptedException e) {                e.printStackTrace();            }        System.out.println(s.get() + " " + getClass().getName());    }}/** * 重量级的多线程框架：ThreadPoolExecutor，维护一个动态线程池 */class UseThreadPoolExecutor {    void go() {        ThreadPoolExecutor executor = new ThreadPoolExecutor(threadSize, threadSize, 1, TimeUnit.SECONDS, new LinkedBlockingDeque<>());        int per = (int) (Math.ceil(1.0 * N / threadSize));        List
    
     
      > futureList = new LinkedList<>();        for (int i = 0; i < threadSize; i++) {            final int ii = i;            futureList.add(executor.submit(() -> {                int sum = 0;                for (int j = ii * per; j < Math.min(N, ii * per + per); j++) {                    sum += j;                }                return sum;            }));        }        int sum = 0;        for (Future
      
        j : futureList) {            try {                sum += j.get(Integer.MAX_VALUE, TimeUnit.SECONDS);            } catch (Exception e) {                e.printStackTrace();            }        }        executor.shutdown();        System.out.println(sum + " " + getClass().getName());    }}/** * ExecutorService：轻量级的线程池 */class UseExecutorService {    void go() {        ExecutorService service = Executors.newFixedThreadPool(threadSize);        int per = (int) (Math.ceil(N * 1.0 / threadSize));        List
       
        
         > futureList = new LinkedList<>();        for (int i = 0; i < threadSize; i++) {            final int ii = i;            futureList.add(service.submit(() -> {                int sum = 0;                for (int j = ii * per; j < Math.min(N, ii * per + per); j++) {                    sum += j;                }                return sum;            }));        }        int sum = 0;        for (Future
         
           j : futureList) { try { sum += j.get(Integer.MAX_VALUE, TimeUnit.SECONDS); } catch (Exception e) { e.printStackTrace(); } } service.shutdown(); System.out.println(sum + " " + getClass().getName()); }}/** * 模拟Linux fork join操作 */class UseForkJoin { void go() { int per = (int) (Math.ceil(1.0 * N / threadSize)); List
          
           
            > a = new ArrayList<>(threadSize); for (int i = 0; i < threadSize; i++) { final int ii = i; a.add(new RecursiveTask
            
             () { @Override protected Integer compute() { int sum = 0; for (int j = ii * per; j < Math.min(N, ii * per + per); j++) { sum += j; } return sum; } }); a.get(i).invoke(); } int s = 0; for (ForkJoinTask
             
               i : a) { s += i.join(); } System.out.println(s + " " + getClass().getName()); }}Main() { new ThreadJoin().go(); new UseExecutorService().go(); new UseThreadPoolExecutor().go(); new UseForkJoin().go();}public static void main(String[] args) { new Main();}}